This invention relates to compositions containing polycarbonate blended with other polymers, and relates particularly to polycarbonate compositions having both improved solvent resistance and improved impact strength.
Polycarbonate has found many uses because, in general, it combines a high level of heat resistance and dimensional stability with good insulating and non-corrosive properties, and it is easily molded. It does, however, suffer from a tendency to craze and crack under the effects of environmental stress, especially contact with organic solvents such as gasoline. Polycarbonate which has crazed is, undesirably, more likely to experience brittle rather than ductile failure. This disadvantage has been somewhat relieved by the practice of blending polycarbonate with various substances such as the olefin polymers polyethylene, polypropylene or polyisobutylene, as described for example in Goldblum, U.S. Pat. No. 3,431,224. These added substances are capable of improving the resistance of polycarbonate to solvents, but they tend to cause an offsetting reduction in the toughness, impact resistance and weldline strength of the blended composition. Additionally, it is frequently found that when the polycarbonate is modified with substances such as polyolefins, the added substances tend to separate in the blend from the polycarbonate and delaminate as evidenced by peeling or splintering. It would accordingly be desirable if substances admixed with polycarbonate for the purpose of improving the environmental stress failure resistance ("ESFR") thereof (e.g. solvent resistance) did not also deleteriously affect its toughness and impact and weldline strength, and cause delamination as evidenced by peeling or splintering.